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  <div class="question_difficulty">
   难度：Medium
  </div>
  <div>
   <h1 class="question_title">
    567. Permutation in String
   </h1>
   Given two strings
   <b>
    s1
   </b>
   and
   <b>
    s2
   </b>
   , write a function to return true if
   <b>
    s2
   </b>
   contains the permutation of
   <b>
    s1
   </b>
   . In other words, one of the first string's permutations is the
   <b>
    substring
   </b>
   of the second string.
   <p>
    <b>
     Example 1:
    </b>
    <br>
   </p>
   <pre>
<b>Input:</b>s1 = "ab" s2 = "eidbaooo"
<b>Output:</b>True
<b>Explanation:</b> s2 contains one permutation of s1 ("ba").
</pre>
   <p>
    <b>
     Example 2:
    </b>
    <br>
   </p>
   <pre>
<b>Input:</b>s1= "ab" s2 = "eidboaoo"
<b>Output:</b> False
</pre>
   <p>
    <b>
     Note:
    </b>
    <br>
   </p>
   <ol>
    <li>
     The input strings only contain lower case letters.
    </li>
    <li>
     The length of both given strings is in range [1, 10,000].
    </li>
   </ol>
  </div>
  <div>
   <h1 class="question_title">
    567. 字符串的排列
   </h1>
   <p>
    给定两个字符串&nbsp;
    <strong>
     s1
    </strong>
    &nbsp;和&nbsp;
    <strong>
     s2
    </strong>
    ，写一个函数来判断
    <strong>
     s2
    </strong>
    是否包含
    <strong>
     s1&nbsp;
    </strong>
    的排列。
   </p>
   <p>
    换句话说，第一个字符串的排列之一是第二个字符串的子串。
   </p>
   <p>
    <strong>
     示例1:
    </strong>
   </p>
   <pre>
<strong>输入: </strong>s1 = "ab" s2 = "eidbaooo"
<strong>输出: </strong>True
<strong>解释:</strong> s2 包含 s1 的排列之一 ("ba").
</pre>
   <p>
    &nbsp;
   </p>
   <p>
    <strong>
     示例2:
    </strong>
   </p>
   <pre>
<strong>输入: </strong>s1= "ab" s2 = "eidboaoo"
<strong>输出:</strong> False
</pre>
   <p>
    &nbsp;
   </p>
   <p>
    <strong>
     注意：
    </strong>
   </p>
   <ol>
    <li>
     输入的字符串只包含小写字母
    </li>
    <li>
     两个字符串的长度都在 [1, 10,000] 之间
    </li>
   </ol>
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